As announced a few days ago, Junya Nakano will be arranging the rest of the soundtrack too. I think his arrangements will be quite minimal like Dawn of Mana's, but he'll probably enhance the timbre of many pieces with his instrument use. The synth is by Hirosato Noda, otherwise known for It's a Wonderful World, Hanjuku Hero VS 3D, Kingdom Hearts II: Final Mix +, Dawn of Mana, Romancing SaGa -Minstrel Song-, Final Fantasy XI, and Front Mission 3.
Here's to hoping the official soundtrack will feature two discs of music rather than cramming everything into one disc with no loops. Based on Square Enix's other efforts, I'm not optimistic.